Annunciator system



April 1953 H. c. WARREN 2,832,068

ANNUNCIATOR SYSTEM Filed Aug. 22. 1956 INVENTOR.

HOWARD C. WARREN ATT 'YS ANNUNCIATOR SYSTEM Howard C. Warren,Northfield, 2 Application August 22, 1956, Serial No. 605,522

9 Claims. (Cl. 340-213 The present invention relates to an aununciatorsystem. More particularly, it has to do with that type of system whichprovides one or more indications of the occurrence of an abnormalcondition or conditions at various difierent places. i

The trend today is toward automation in industrial station is meansresponsive to the occurrence of a predeplants and processes, and as aresult, machinery in large p problems, as for example, the absence ofpersonnel in constant attendance to the machinery and systems whichwould be alerted when abnormal conditions or malfunctioning existstherein and that could then apprise the proper personnel of suchconditions. To overcome this disadvantage, annunciator or alarm systemshave been developed for use :with automatic equipment and that isoperative to provide warnings whenever abnormal conditions are presentin the equipment. tems for the most part have been custom made toaccommodate particular conditions in given installations, and have beencomplex and quite expensive. There exists then a need for an alarm oraununciator system that is simple. in design and relatively inexpensiveand that can be made to accommodate a large variety of differentequipment installations.

' It is, accordingly, the general object of the present invention toprovide a. new and improved annunciator system which is simple toconstruct and install, which requires a minimum of maintenance, in whichthe components are economical and small in size, and in which the amountof necessary wiring is minimized.

- It is 'anotherobject of the present invention to pro- Knownaununciator sysvide an aununciator system which employs a minimum ofmovingparts and in'which the remote parts of the system need not besealed or otherwise protected against the effects of dust, contaminationor corrosive atmospheres. Another object of the present invention is toprovide an aununciator system which is capable of use interchangeablywith alternating and direct current power sources.

A further object of the present invention is to provide an aununciator.system in which there are no relays at the detecting stations.

A, still further object of the present invention is to providean'improved' aununciator system in whicha single, silenceable,indication device is operated in response to the occurrence of any oneof a number of conditions happening at various different places andwhich, subsequent to providing an indicationo'f the occurrence of onesuch condition,- may be placed in readiness to detect the occurrence. ofanother condition even though the first con-' to current of a valuewithin a predetermined range oi:'

values. At a station usually remote from the monitoring Also, preferablyat the monitoring sta-- termined condition for supplying current to thefirst utilization device of g a value within the selected range ofvalues; subsequent to the occurrence of the condition, means responsiveto the'continuance of the condition changes the first-utilization-devicesupply-current to a value without the selected range of values and alsoetfects current supply to the second utilization device of a valuewithin the predetermined range of values.

In a corollary aspect of the invention, additional means maintains theresponse of the first utilization device subsequent to the occurrence ofthe condition. Means is included in the system for disabling theresponse maintaining means subsequent to reduction of thefirst-utilization-device supply-current to the value without theselected range of values. Thus, the first utilization device is capableof being disabled without effecting the operation of thesecondutilization device.

. The aununciator system of the present invention finds itsgreatestutility when the system is applied to the detection of anyof anumber of different possible condition occurrences. In this aspect ofthe invention, a plurality of means each responsive to the occurrenceofan individual one of aplura'lity of conditions individually supplycurrent to a utilization device of a value within a selected range ofvalues that efiect response of the utilizationdevice. There is provideda plurality of means each responsive to the continuance of an individualone of the conditions for individually changing the respectiveindividual utilization-device supply-current to a value without theselected range of values subsequent to the occurrence of the respectiveindividual one of the conditions.

The features of the present invention which arebelieved to be novel areset forth with'parti-cularity in appended claims. The organization andmanner of operation of the invention, together with further objects andadvantages thereof may thus be understood with reference to thefollowing description taken in connection with the accompanying drawing,in which the single figure is a schematic diagram of an aununciatorsystem incorporating the present invention. i

In the embodiment shown in thedrawing, for purposes of illustration,either an alternating or a unidirectional current power supply.isconnected between a pair of power lamps 13 and diode 14; a normallyopen contact 22 is connected between line 10 and the junction betweencontacts 15 and coil 16. An electrically-operated horn 23 is connectedin series with a normally-open contactpair 24across lines 10 and 11. Inseries connection between line 10 and the junction between diode 14 andcontacts 15 is another trouble contact pair 12', another indicator lamp13 and another diode 14; contacts 12"are shunted by'a normally-open testswitch 20'. *A negative-cotlicient thermistor 21 ,is connected betweenline 11 and the junctionbetween lamp '13 and diode 14'.

The inventive circuit includes a first utilization device responsiveonly to current of a value within a selected range of values; such adevice is one that is responsive only to current of-a value in excess ofa'threshold value.

.To this end, horn 23 is energized upon the closure of= contacts 24 byvirtue of the, passage through coil 16 of-- a current value in'excess ofa'selected threshold value.

An additional, second utilization device is responsive only to currentof a value within a predetermined range of asaaoss values; such a deviceis one that responds only to current of a value in excess of apredetermined value. This characteristic is present in lamps 13 whichaflFords a visual indication only when the lamp is conducting current;in most instances more than a certainminirnum current is required toactually provide an indicationcapable of being seen by the human eye,although some well-known varieties of lamps will glow upon a verysmallamount of current conduction.

Also included is means responsive to the occurrence of a predeterminedcondition for supplying current to the first utilization device of avalue within the selected range of values. Thus, upon the closure oftrouble contacts 12 by the happening of an abnormal condition, currentof a value sufiicient to actuate the relay, comprising coil 16 andcontacts 24, flows from line through contacts 12, lamps 1'3, diode 14,closed contacts 15, coil 16, and switch 17 to line 11. I

The system includes means responsive to the continuance of the conditionfor changing the first-utilizationdevice supply-current to a valuewithout the selected range of values subsequent to the occurrence of thecondition and for effectingcurrent supply-to the second utilizationdevice of a value within the predetermined range of values to which thatdevice responds; accordingly, closure of contacts 12 impresses apotential across negativecoeflicient thermistor 21. It will be observedthat thermistor 21 is coupled in parallel with coil 16, the primary orfirst utilization device, and in series with lamps 13, the secondary oradditional utilization device. Upon the continuance of closure ofcontacts 12, the resistance of thermistor 21 decreases from an initialhigh value to a comparatively low value. When contacts 12 are firstclosed, the resistance of thermistor 21 is sutficiently high to permitcurrent flow through coil 16 of a value in excess of that thresholdvalue necessary to close'contacts 24-. However, subsequent to theclosing of contacts 12, the resistance of thermistor 21 becomessufficiently low that the thermistor effectually shorts coil 16,diverting current therefrom through the thermistor whereupon the currentin coil 16 is reduced below its threshold value and contacts 24 openthereby deenergizing horn 23. The current flow through thermistor 21 isalso sufiicient to effect lighting of the lamp 13 so that a visualindication remains as long as the detected condition persists andcontacts 12 thus remain closed. Thus, it will be observed that, as Sofar described, the detection of a condition results in almost immediateenergization of horn 23 and at least very quick. lighting of lamps 13,subsequent to the happening of the condition, the increased current flowin thermistor 21 becomes sufficiently large that an insuflicient amountof current is available by way of contacts 12 to maintain energizationof coil 16 and hence of horn 23.

In accordance with a further aspect of the invention, the response ofthe first utilization device is maintained subsequent to the occurrenceof the detected condition; in addition, this response-maintaining meansmay subsequently be disabled. Accordingly, contacts 15 and 22 are alsoactuated upon the energization of coil 16 by current in excess of itsthreshold value; upon actuation of the relay, contacts 15 open andcontacts 22 close, thus providing a holding or seal-in circuit for coil16. Therefore, as soon as contacts 12 close to effect actuation of therelay, the coil circuit is switched so as to be connected directlybetween lines 10 and 11 rather than in series with the trouble contactsand the lamp. Thus, born 23 remains energized even though thermistor 21decreases in resistance value to a point such that it would comprise ashort circuit around coil 16 but for the opening of contacts 15 witheifectation of the holding circuit. Upon subsequent depression of switch17, as by the action of attending personnel at the monitoring station,the circuit for coil 16 is broken whereupon contacts 24 opendeenergizing horn 23, contacts 22 open disabling the holding circuit,and contacts 15 reconnect coil 16 into the trouble contacts, lamp andthemistor circuit. However, if switch 17 is depressed after thermistor21 has decreased in resistance value by an amount such that thethermistor forms a low resistance path around coil 16, current in excessof the threshold value is prevented from flowing through the coil. Thus,the relay including coil 16 is not reactuated upon subsequent closure ofswitch 17 even though coil 16 again is coupled in series with the closedtrouble contacts between the power lines., Note that lamps 13 continueto provide a visual indication of the presence of the condition eventhough the holding circuit has been disabled.

The utility of the invention is enhanced in accordance with anotheraspect thereof which includes a first utilization device of the abovedescribed character and which preferably includes a plurality ofadditional utilization devices all having the above-mentionedcorresponding characteristic of the second utilization device. Aplurality of condition-responsive means, each similar to those abovedescribed, are individually capable of supplying current to thefirstutilization device of the required amount. There is also provided aplurality of means each responsive to the continuance of an individualcondition for individually changing the respective individualfirst-utilization-device supply-current value to a value without theselected range of values subsequent to the respective conditionoccurrence and for individually effecting current supply of thenecessary amount to the preferably included individual ones of theadditional utilization devices. To this end, closure of contacts 12'upon the occurrence of the condition detected by those contactscompletes a supply circuit for coil 16 for supplying current thereto ofan amount in excess of its threshold amount in a manner identical tothat above described upon the closure of contacts 12. 'Likewise,thermistor 21 operates in a manner identical to that of thermistor 21 toreduce the amountof supply current available to coil 16 below thatnecessary for actuation of the relay and for effecting sutficientcurrent flow in lamps 13 to provide a visual indication. It will beobserved that there may be any number of the trouble contacts eachhaving a lamp and a thermistor. Diodes 14 and 14' are inserted toprevent interference between the operation of one thermistor circuitwith that of the next; for example, without the diodes, a decrease inthe resistance of thermistor 211V0l11d establish an effectual shortcircuit in parallel with thermistor 21 to. prevent its operation uponthe closure of contacts 12'. However, diode 14 has the effect ofdisposing thermistor 21 as a short circuit, during closure of contacts12, only withrespect to the circuit of contacts 12 and completelyindependent of contacts 12. Thus, the function of the diodes is topermit thermistor 21 to divert away from coil 16 only current flowingthrough the series coupled contacts 12. Therefore, after an initialdetection by contacts 12 effecting actuation of the relay, thesubsequent deenergization of the relay upon opening of switch 17 placesthe circuit of coil 16 back into readiness to receive the current fromthe circuit of contacts 12' should those contacts be closed whilecontacts 12 remain closed. Hence, each of the trouble contact circuitsis independent and isolated from all of the others, all provide arespective individual visual indication, and any. one of them will causeenergization of horn 23 if it is not already energized.

Of course, closure of test switch 20, at any of the remote stations tobridge contacts'12 enables a determination by the operating personnelthat all is in order. Closure of the test switches causes operation ofthe circuit in a manner identical with that above described for closureof contacts 12.

Thus, the annunciator system requires a minimum of moving parts; thereare no relays necessary at the remote stations. This avoids having to.provide hermetically-sealed units and insures extremely long life anddurability of the system. It should be noted that this system may beused interchangeably'on either alternating or unidirectional currents;the operation is the same in either case. Such a system is economical tomanufacture and install, the cost of thermistors being much less thanthat of relays usually employed in such systems at the remote stations.Also, the elements employed in the annunciator system need only requirea minimum of space and therefore installation is an exceedingly simpleproblem. Any number of remote stations may be utilized all common to asingle hornor the like which may be silenced by a single push-button. Ifdesired, of course, visual indication at the remote station may bedispensed with, the present invention still having great utility inbeing able to actuate a single, individually silenceable utilizationdevice upon the occurrenceof any of a number of conditions atwidely-spaced detection points- While a particular embodiment of thepresent invention has been shown and described, it would be obvious tothose skilled in the art that changes and modifications may be madewithout departing from the invention in its broader aspects.

I claim:

1. In an annunciator system for signalling changes in condition of adevice policed thereby: a relay equipped with a pair of normally closedcontacts and with two pairs of normally open contacts one of the latterof which is connected in series with said relay to provide therewith aself-holding relay circuit; an audible signal device connected in serieswith the other of said normally open contacts and defining therewith anaudible signal circuit in parallel with said relay circuit; a visualsignal circuit connected in parallel with the aforesaid circuits andcomprising a visual signal device, a normally open single-pole,single-throw control switch in series with said visual signal device andadapted to be actuated by such a change in condition, and a negativecoefiicient thermistor also in series therewith; and a relay energizingcircuit in shunt connection with said thermistor and comprising withsaid relay a diode connected to said visual signal device and poled topermit current to flow therefrom, and said normally closed contactconnected between said diode and said relay; said thermistor beingcharacterized by having a resistance that progressively decreases invalue as current flows therethrough to a .value such that the resultantdivision of current flow between said energizing circuit and thermistoris preponderant through said thermistor and falls in said energizingcircuit to a value less than that required-to energize said relay.

2. The annunciator system of claim 1 in which a plurality of visualsignal circuits and energizing circuits therefor are provided inparallel with each other; and in which a normally closed, manuallyoperable switch is connected in series in said self-holding relaycircuit for deenergizing said relay subsequent to each energizationthereof to thereby ready the same for actuation by another of saidvisual signal circuits. s

3. In an annunciator system for signaling change in condition of adevice policed thereby: a relay circuit including a relay-havingcontacts in self-holding connection therewith; a signal device connectedwith said relay for actuation when the relay is energized; a signalcircuit connected in parallel with said relay circuit and comprising asecond signal device, a control switch connected therewith and adaptedto be actuated by such a change in condition, and a variable resistancedevice connected to said visual signal device; and a relay energizingcircuit in shunt connection with said variable valued resistance deviceand comprising with said relay a uni-directional current conductorconnected to said second signal device; said variable valued resistancedevice being characterized by having a resistance that progressivelydecreases in value as current flows therethrough to a value such thatthe resultant division of current flow between said energizing circuitand resistance device is preponderant through said resistance device andfalls in said energizing circuit to a value less than that required tomaintain said relay in an energized state.

4. The annunciator system of claim 3 in which said variable valuedresistance device is a negative coefficient thermistor.

5. The system of claim 4 in which said control switch is a single-pole,single-throw switch.

6. In an annunciator system adapted for use in signalling a change ofcondition in a plurality of devices policed thereby: aself-holding relaycircuit including a relay and a switch for selectively interrupting thecircuit; a first signal device connected with said relay for actuationupon energization thereof; a plurality of signal circuits each having asecond signal device therein, a variable valued resistance deviceconnected therewith; and a control switch alsoconnected with said secondsignal device, each of said control switches being adapted to beactuated by a change in the respective conditions policed by saidsystem; and an actuating circuit for each of said signal circuits andeach being connected with said relay for selective energization thereof,each of said actuating circuits including said relayas an elementthereof and being selectively connected in shunt with said variablevalued resistance devices; each of said variable valued resistancedevices being characterized by having a resistance that decreases invalue as current flows therethrough to a value such that the resultantdivision of current flow between it and the associated energizingcircuit becomes preponderant through said resistance device and falls inthe energizing circuit to a value less than that required to energizesaid relay.

7. The system of claim 6 in which each of said variable valuedresistance devices comprisesa thermistor.

8. The system of claim 6 in which each of said energizing circuitsincludes a uni-directional current flow device.

9. The system of claim 8 in which each uni-directional current fiowdevice is a transistor.

References Cited in the file of this patent UNITED STATES PATENTS2,501,793

